Spearfish frequency identification

[spearfishian]

Hey all, I'm still such an armature so please forgive if these questions are silly.

I'm in the Spearfish area and I've encountered two very strong transmitters who constantly overload my SDR unless I turn the gain really low.
The first is 159.495 which is a local bus company, found the license etc. I guessed this one.
The second is 159.539 (159.540?), I can't find an associated license for that frequency. This one is REALLY strong. It sounds like the same type of radio traffic.

Am I forgetting to look somewhere to see who it is? What am I missing?

Also, I don't think there is....but is there anything a person can do to reduce an overpowering signal like this, other than lower gain levels?
My antenna can get great signal from Crook County all the way to some of Pennington (darn hills) but this one just drowns them out.

Thank you for any input!

 

[ecps92]

Hey all, I'm still such an armature so please forgive if these questions are silly.

I'm in the Spearfish area and I've encountered two very strong transmitters who constantly overload my SDR unless I turn the gain really low.
The first is 159.495 which is a local bus company, found the license etc. I guessed this one.
The second is 159.539 (159.540?), I can't find an associated license for that frequency. This one is REALLY strong. It sounds like the same type of radio traffic.

Am I forgetting to look somewhere to see who it is? What am I missing?

Also, I don't think there is....but is there anything a person can do to reduce an overpowering signal like this, other than lower gain levels?
My antenna can get great signal from Crook County all the way to some of Pennington (darn hills) but this one just drowns them out.

Thank you for any input!

159.5400 would be the exact FCC allocation, unless you are picking up the adjacent channels +/- of 159.5325 and 159.5475

 

[nolinger]

Google notch filters.

 

[Rlahey]

Im guessing that your SDR dongle is either drifting frequency a touch, or getting over powered by the SD State P25 Link Terry Peak control channel

1 (1)

014 (E)

Lead (Terry Peak)

Lawrence

159.600c

Terry Peak should have excellent coverage into Spearfish, and the frequency of the dongle might not be spot on, mine never is.

 

[spearfishian]

Thanks for the replies.
I'm learning about notch filters, just new to it etc The physical ones I can find for SDRs are all for FM. Trying to learn about software based ones.
Rlahey, I thought that as well. The Terry Peak site frequencies aren't close to this one though...and for testing I had another scanner monitoring it (again, SDR, so I could see when it was sending 'data' as well as voice) The only correlation between the overloading and another transmission is the one I listed.

Is it possible the transmission I'm hearing is actually from another frequency? I don't know what its called in radios but I think of it like an overtone, or resonance (in music).

Sorry for being so confusing about this! Its not a huge deal I'm just trying to learn how to sleuth out who is transmitting when I can't find that frequency listed to anyone nearby me.

Also, just for fun I'm gonna attach a screen shot of the SDR spectrum when it happens! Thank you everyone.

 

[Rlahey]

I believe that your SDR may be off frequency by a few megahertz. I still have have high, high suspicion that what you are seeing on your screen or actually control channels for the trunked radio network. Can you provide an audio sample of them? That will provide definitive diagnosis. If these carriers are there all the time, not just intermittently, I would bet money that they are trunking control channels. SDR dongles can be troublesome and need tuning. I’ve never had one be spot on In frequency. I always have to adjust my software for the drift in the dongle.

 

[spearfishian]

Rlahey, I was thinking that too and playing around with the correction.
Then I was sent a reminder of the fcc license search (which I did before). Decided to look again.
I was filtering out expired licenses, but didn't this time. Found a local concrete business has listed on their frequencies the one I was looking for 159.540 So I guess that is probably it. Just maybe they forgot to renew.
I'm only confused because if that IS them the locations listed for that frequency aren't nearby. There IS one of their industrial facilities just across the interstate, just a couple thousand feet away. A station class of FX1 is a control station...so they probably have a repeater there and this is what I've been looking for. Am I way off?

Anyway, thanks for helping out this AMATURE radio enthusiast

(on edit, did street view 'spying' sure enough there is an antenna. Plus a yagi style antenna pointing right at my antenna. oof!)